LOS ANGELES (CBSLA) – If you’re one of the more than three million Californians who have already obtained a Real ID, your work is likely not yet done.

According to the Sacramento Bee, the Department of Homeland Security sent a letter Monday to California Gov. Gavin Newsom informing him that the DMV is not meeting standards regarding the number of documents applicants must show to prove residency as part of the REAL ID application process.

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An example of a California REAL ID. (CBS)

The California DMV has been issuing REAL IDs since January of 2018. However, the confusion began last November, when DHS informed the DMV that its procedure for approving REAL IDs was incorrect.

To obtain a REAL ID, applicants must show two documents proving residency, such as a utility bill or a pay stub. The California DMV said it had been operating under a directive from DHS that applicants only be required to physically bring in one document proving residency to the DMV office, and counted on delivery of the ID card by the post office as the secondary proof of someone’s address.

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Emails show that DHS had approved such a process in 2017. However, in November, DHS suddenly reversed course, and told the DMV that was no longer acceptable: applicants must now bring two documents proving residency in person to a DMV office.

In response to this week’s DHS letter, the DMV released a statement to the Sacramento Bee saying it will reach out to the 3.4 million Californians who have already obtained REAL IDs and inform them that they will need to provide a second proof of residency form.

Those people will not need to come back into the DMV, however. Instead, the DMV will mail them letters that they need to mail back, thus fulfilling the DHS guidelines for a second proof of residency.

“The DMV will be sending letters to individuals who submitted one proof of residency to acquire their Real ID card, informing them to send the letter back to DMV to serve as their proof of second residency,” the DMV statement read.

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By October of 2020, REAL ID cards will required to board airplanes or enter federal buildings. U.S. residents who do not have a REAL ID will be required to show an alternative document, like a passport.